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ssf
Structure functions of a scalar field, histograms of increments

Description ```STFUN = ssf(F,DIM) computes the structure functions of the scalar field F and the histograms of the scalar increments along the dimension DIM (with DIM=1, 2, or 'x','y'). If F is an array of fields, the structure functions are averaged over the fields. Structure functions of order n are the moments of the scalar increments as a function of the separation r, <(s(x+r) - s(x))^n>. The structure STFUN contains the following fields: - r : separation lengths (in mesh units) - unitr: unit of separation length (e.g., 'mm') - scaler : scale (in physical units) of a unit separation - sf : R-by-ORDER matrix containing the structure functions of order ORDER. - sfabs : idem as sf, with absolute values. - skew: skewness factor. - flat: flatness factor. - bin : bins for the histograms - binwidth: width of a bin - hsi : (R x BINVEC) matrix containing the histograms of scalar increments. - pdfsi : normalized histograms (PDF). - history: remind from which field vsf has been called. - n: nbre of points used in the computation. - nfields: nbre of fields used in the computation (given by LENGTH(S)). STFUN = ssf(S, 'PropertyName', PropertyValue, ...) also specifies the optional input arguments: - 'bin', BIN : vector where velocity increments should be bined. By default, 1000 bins are taken, chosen from the rms of the first field. - 'r', R : list of separations delta_r over which increments are computed, given in mesh units (should be smaller than the largest extent of the field). If not specified, a default separation list is used. - 'maxorder', ORDER: maximum order of structure function (usually between 4 and 8). ORDER=4 is taken by default (although its convergence may not be guaranteed). By default, ssf considers the values 0 as erroneous, and does not include them in the histogram. If however the values 0 are to be included, specify vsf(...,'0'); Example v = loadvec('*.vc7'); stfun = ssf(filterf(vec2scal(v,'rot'))); See Also vsf, vsf_disp, histf, corrf, specf. Published output in the Help browser showdemo ssf ```
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